Automatic shutter mechanism for pitot tubes



NOV. 22, 1949 EASTERDAY 2,488,810

AUTOMATIC SHUTTER MECHANISM FOR PITOT TUBES Filed May 25, 1946 A T TOR/V57.

Patented Nov. 22, 1949 UNITED STATES TENT OFFICE AUTOMATIC SHUTTER MECHANISM FOR PITOT TUBES 3 Claims.

This invention relates to air speed measuring and indicating instruments for aircraft, and

'more particularly to a device for automatically closing, or uncovering the air inlet opening of the Pitot static tube of such an instrument for protecting and operating said instrument as required.

The general object of the invention is to provide a device for automatically closing the air inlet opening of the Pitot static tube of an air speed measuring and indicating instrument on an airplane, when the plane lands on the round, and for automatically uncovering said opening, as the plane gains speed in taking off from the ground, whereby air and the elements are prevented from entering said tube through said opening and damaging said instrument, while the plane is on the ground, and air is admitted into said Pitot tube to operate said instrument to measure and indicate the wind speed as the plane flies.

Other objects and advantages will appear hereinafter as this specification progresses.

The invention is illustrated in the annexed drawing, which forms a part of this specification, and in which:

Fig. 1 is a side elevation of a wind speed measuring and indicating instrument embodying my invention, shown mounted on a wing of an airplane.

Fig. 2 is a side elevation of a wind-speed measuring and indicating instrument embodying my invention, with my invention shown in position closing the air-inlet opening of the Pitot tube of said instrument.

Fig. 3 is a plan view of Fig. 2.

Fig. 4 is a view like Fig. 2, except that my invention is shown in position uncovering the airinlet opening of the Pitot tube of the wind-speed measuring and indicating instrument.

Fig. 5 is a front end elevation of Fig. 2.

Fig. 6 is a front end elevation of Fig. 3.

Referring more particularly to the drawing, in which the same parts are designated by the same reference numerals, I designates a windspeed responsive instrument including a Pitot tube 2 provided with an air-inlet opening 3 in its forward end, which instrument is shown mounted in the forward edge of a Wing 4 of an airplane 5 in Fig. 1 of the drawing.

My invention includes generally a shutter 6, a shutter shaft 1, a plunger 8, a plunger tube 9, a plunger spring ID, a shaft and plunger coupling H, a wind pressure plane l2 upstanding from said coupling, a clamp bearing [3 for said shaft l and a mounting clamp It for said plunger tube 9. The shutter 6 comprises a flat strip of spring steel shaped to extend forwardly and downwardly over the forward end of the Pitot tube 2 and over the air-inlet opening 3 in said end of said Pitot tube.

The coupling ll couples the rear end of the shutter shaft l and the forward end of the plunger 8 in axially offset relation, as shown in Fig. 3.

The clamp bearing [3 includes a depending clamp 15 comprising a pair of arcuate spring clamp members is, the end portions I! of which members are bent outwardly, and through which end portions are extended clamp bolts I8, on the ends of which are threaded nuts I9. The bearing I3 is clamped on the forward portion of the Pitot tube 2, above said tube coaxially therewith by the clamp l5, the members E6 of which clamp are extended downwardly around the sides of said Pitot tube and clamped around said tube by the clamp bolt 18 and nut l9, which are tightened against the lower end portions I! of said clamp members.

The mounting clamp 14 comprises a pair of depending arcuate spring clamp members 20, the end portions 2| of which are bent outwardly and through which are extended a clamp bolt 22, on the end of which is threaded a nut 23. The plunger tube 9 is clamped by the clamp I4 on the Pitot tube 2 rearwardly of the bearing l3 and clamp l5 and above said Pitot tube, and to one side of the clamp bearing 13, the members 20 of said clamp I4 extending downwardly around the sides of said Pitot tube and being clamped around said tube by the clamp bolt 22 and nut 23, which are tightened against the lower end portions 2| of said clamp members. The offsetting of the plunger 8 to one side of the shutter shaft 1 and the clamping of the plunger tube 9 to one side of the clamp bearing I3 on the Pitot tube 2 to receive said plunger, prevents the shutter shaft 1 from turning in its bearing 13 and thereby maintains the shutter 6 in alignment with the opening 3 in the forward end of the Pitot tube 2 and the pressure plane 12 in an upright position above said tube in operative position.

The plunger spring Ill is located in the plunger tube 9 with its rear end bearing against the closed rear end 24 of said tube and its forward end bearing against the rear end of the plunger 8, which spring urges said plunger, pressure plane I2, shutter shaft 1 and shutter 6 forwardly and normally maintains the forward end of said shutter in position over the opening 3 in the forward end of the Pitot tube 2, closing said opening.

The operation of my invention is as follows:

When the airplane 5 is on the ground the airinlet opening 3 in the forward end of the Pitot tube 2, is closed by the shutter 6, which is projected forwardly over said openin by the plunger sprin It through the medium of the plunger 8, coupling I l and shutter shaft 1.

When the plane 5' gains speed in taking ofi from the ground the pressure of the air against the pressure plane I2 forces said plane, together with the coupling ll, shaft I, shutter 6 and plunger 8 rearwardly agains'tthgtirs'ion of the spring l6, which is compressed by said plunger until said shutter is withdrawn rearwardly from over the air-inlet opening 3 in th'forw'a'rd end of the Pitot tube 2, uncovering sai'd opening and allowing the air to pass therethrough, into said Pitot tube to operate the wind-speed measuring and indicating instrument I to measure and indic'ate the'wind' speed through which the plane When the plane lands the pressure of the air against the pressure planefll is reduced, so that the spring Ill forces the Plunger 8 together with the coupling and pressure plane l2; shaft '1 and shutter '6' forwardlyniitil said'shutter is projected over and closes the opening 3 in the forwarde'rid ofthe Pitot tube '2, preventing the air and the elements from entering the Pitot tube through said opening and thereby protecting the wind-speedresp'ons'ive instrument I from the air and'the elements.-

Iclaim'f 1. In'combinationwith a wind-speed measuring and indicating instrument including a Pitot tube provided with an air-jimet opening in'its forward end, a shutterslidably mounted' on'said Pitot tube, said shutter oomprisingafiat stripof spring material shaped to extend'forwardly and downwardly I a plunger tube clamped on said Pitot tube, a shutter comprising a flat'strip of spring metal shaped to extend forwardly and downwardly over the forward end of said Pitot tube and over said airjinlet opening, a shaft slidable in said clamp hearing; to the forward end of which shaft said shutter is rigidly secured at its rear end, a plunger connected to said shaft and slidable in said plunger tube, a spring in said plunger tube for o c n s d plun e o th r W hsa ds a t and said shutter forwardly so that said shutter will cover said air inlet opening in said Pitot tube, and a wind pressure plane mounted on saidshaft a d s d un er to bead-ed upon by W nd pressure to force said plunger rearwardly against, the tension of said springtogether withsaid shaft d u t r unti aid shutter unc ve sl aid i -in et o e ng nlsaid P tt u e.

3. The combination characterizedby claim 2 in which the plunger and plunger tube are ofiset laterally from said shaft and saidbearing tovprevent turning of said shaft insaid'bearing,

KARL EASTE DAY- REFERENCES CITED,

The following references are of; record in the file of this patent:

UNITED STATES PA'I'ENI' S Z Numb er Name v Date 948,872 Clark Feb. 8,; 910

FOREIGN PATENTS Number Country- 7 Date 9. 3 Grea ta --.---,V--. n,- 2 93. 

